Some scientific studies are popular from the start, garnering multiple citations from other researchers. But others can languish as 'sleeping beauties' for more than a century before awaking to glorious approval, a study finds1.

Filippo Radicchi, a researcher in complex networks at Indiana University Bloomington, and his colleagues have analysed a set of 22 million scientific papers to identify such beauties — and to find the fairest of them all.

The rate at which papers acquire citations generally declines after an initial period of growth. Previous research shows that the fate of a paper can often be determined based on how many citations it attracts in its first five years.

But some papers lie dormant for years before experiencing a sudden spike in citations as they are discovered and recognized as important. In 2004, bibliometrics expert Anthony van Raan of Leiden University's Centre for Science and Technology Studies in the Netherlands labelled this the ‘sleeping beauty’ phenomenon2. Perhaps the most famous example is a 1935 quantum-mechanics paper by Albert Einstein, Boris Podolsky and Nathan Rosen, which rested unloved for decades3.

Quantified beauty

Radicchi and his colleagues came up with the 'beauty coefficient', B, a value based on the number of citations a paper has received and how long after publication it gained them. A paper that accrues citations linearly over time scores 0, but one that languishes for 100 years before rising to fame could score higher than 10,000, the researchers report in the Proceedings of the National Academy of Sciences.

Topping the team’s list, with a B value of 11,600, is ‘Concerning adsorption in solutions’, research published in 19064 that did not awaken until 2002. The famous Einstein–Podolsky–Rosen paper comes in 14th place, with a B value of 2,258. The longest sleeper in the top 15 is a statistics paper from Karl Pearson, entitled, ‘On lines and planes of closest fit to systems of points in space'. Published in Philosophical Magazine in 19015, this paper awoke only in 2002.

Top 15 'sleeping beauties'

Table 7.26538 Top 15 'sleeping beauties'

In many cases, the beauty phenomenon occurs when research finds application in a field outside its own, says Radicchi — such as statistical methods that become useful in biology.

Van Raan says that the “beauty coefficient is certainly an innovative index” that echoes his earlier ‘Grand Sleeping Beauty Equation’, which calculates the number of such papers for a given sleeping time and other variables.

Van Raan is now focusing on issues such as the factors that produce sleeping beauties, and whether the papers are 'one-hit wonders'. If some scientists produce more than one sleeping beauty, that would indicate a well-planned research theme, rather than an unexpected hit.

Rise and shine

For his part, Radicchi says that he is trying to identify the ‘princes’ — the papers that wake up sleeping beauties from their slumbers with an important citation.

Dashun Wang, an information scientist at Pennsylvania State University, University Park, says that the new work is “a very fundamental piece in the field of science of science”. It may eventually help explain why his model to predict the trajectory of a paper from its early citations6 does not work for around 6.5% of papers. And understanding sleeping beauties, says Wang, will assist the understanding of citation dynamics in general.

“One important conclusion of this paper is that, while the fraction of sleeping beauties may be well within the 6.5% of papers, they are not as rare as we had previously thought,” he says. “These sleeping beauties are now being systematically discovered thanks to the new method proposed in this paper that is rather convincing and does not rely on arbitrary thresholds."

However, Radicchi cautions scientists not to hold out too much hope that their forgotten publications are sleeping beauties, given many papers are never cited: “I expect, if you look at a paper that is 10 years old [and not cited], my guess is it will continue to have zero citations forever.”